1. Field of the Invention
The present invention relates to novel silico-titanate compositions of matter, and methods of making and using such compositions.
2. Background Art
Synthesis of molecular sieves and zeolite-type materials are known to the prior art. The crystalline structure of such materials permits cation or anion exchange (or both) as well as water molecule exchange. Further, such materials not only separate molecules of different size, but are capable of segregating molecules of the same size but of different electrical charge.
Among other uses for molecular sieves, or zeolite-type materials, are as "carriers" for certain volatile catalysts, facilitating chemical reactions. The catalysts are trapped and thereby retained in the zeolite molecular structure during the chemical process. Channelized zeolite-type materials resembling tectosilicates, however, are not the only structures that can effect ion exchange. Several phyllosilicates of clay-like materials, for example, montmorillonite (smectite) and vermiculite, readily exchange cations between the tetrahedral layers.
Syntheses of silicon titanate zeolite-type materials is known to the art. U.S. Pat. No. 3,329,481 to Young, entitled Crystalline Titano-Silicate Zeolites, discloses several Group IV-B metallo-silicate zeolites wherein the metal may be a monovalent or bivalent metal, as well as ammonium or hydrogen.
U.S. Pat. No. 4,938,939, to Kuznicki entitled, Preparation of Small-Pored Crystalline Titanium Molecular Sieve Zeolites, discloses a process of producing crystalline titanium zeolite-type compositions having a pore size of 3-5 Angstroms.
U.S. Pat. No. 4,853,202, also to Kuznicki, entitled Large-Pored Crystalline Titanium Molecular Sieve Zeolites, discloses methods of making crystalline titanium molecular sieve compositions having a pore size of about 8 Angstroms.
"The OD Structure of Zorite" Sandomirskii et al., Sov. Phys. Crystallvgr., 24(6), Nov-Dec. 1979, discloses the crystallographic structure of a naturally occurring alkaline titanosilicate found in Siberia.
U.S. Pat. No. 5,015,453 to Chapman entitled Crystalline Group IVA, Metal-Containing Molecular Sieve Compositions, discloses titanium-silicates, phosphates and phosphosilicates which are three-dimensional microporous crystalline structures.
"The Crystal Structure of a New Natural Sodium Titanosilicate," by E. V. Sokolova et al., Sov. Phys. Dokl., 34(7), 583-585, July 1989, describes a naturally occurring material, sitinakite, found in the former Soviet Union having an empirical chemical formula of (Na.sub.2.251 R.sub.0.693 Ca.sub.0.004 Sr.sub.0.062 Ba.sub.0.026 Ce.sub.0.004).sub..SIGMA.3.04 .times.(Ti.sub.3.56 Nb.sub.0.195 Fe.sub.0.014 Zr.sub.0.006).sub..SIGMA.403 Si.sub.1.928 O.sub.13 (O.sub.0.45 H.sub.0.955).sub..SIGMA.1.00 .times.3.7 H.sub.2 O which, as an idealized formula, comprises Na.sub.2 (H.sub.2 O).sub.2 [(Ti.sub.4 O.sub.5 (OH) (SiO.sub.4).sub.2 ]K(H.sub.2 O).sub.1.7. Within this material specimens having higher Nb impurity contents are speculated to have an orthorhombic symmetry.